顶板岩层破断诱发矿震的频谱特征

 揭示顶板破断过程中的微震活动规律，采用频谱演变来评价顶板动力危害的强度，并进一步监测顶板的破断。采用SOS微震监测系统，针对坚硬以及软弱顶板破断来压的过程进行了实测，取得如下结论：(1) 顶板破断之前，低频段微震幅值逐渐增加，来压时信号的幅值达到最大值，之后产生突降。同时微震前兆信号主频与来压强度呈负相关。(2) 软弱顶板破断之前，微震信号主频开始向低频段移动，但前兆主频均大于20 Hz，来压之后主频又开始向高频段移动。(3) 坚硬顶板破断过程极其短暂，主震信号幅值较高，但主频小于5 Hz，来压前后低频微震信号的幅值较低，前兆效应不明显。利用上述规律，可以对顶板破断的过程及其强度进行有效的评价和预测。

FREQUENCY-SPECTRUM CHARACTERS OF MICROSEISMIC SIGNALS INDUCED BY ROOF STRATUM FRACTURE

To evaluate and monitor the danger and intensity of roof dynamic fracture by the evolution rules of frequency-spectrum，the research on microseismic(MS) activity rules in the process of roof fracture is presented. With SOS MS monitoring system，the hard and weak roof fracture processes are measured in field. The achieved results are as follows. (1) Before the roof fracture，the amplitude of MS signals in the low-frequency band increases gradually；then it reaches the maximum value at roof fracture and pressurization；after that，the amplitude begins to decrease quickly. Simultaneously，the correlation between precursory signal main frequency and the pressurization intensity is negative. (2) Before the weak roof fracture，the main frequency of MS signals begins to move to the low-frequency band，but the main frequency of precursory signals is larger than 20 Hz. After roof pressurization，the main frequency will move to the high-frequency band. (3) The process of hard roof fracture is transient，and the amplitude of main shock signals is higher，but the main frequency is lower than 5 Hz. Amplitude in the low-frequency band before and after fracturing is lower，and the precursory effect is not obvious. With above rules，the process and intensity of roof fracture and pressurization can be evaluated and predicted effectively.